The effort is complementary to studies by NASA's Kepler space telescope, which hunts for extrasolar planets around sun-like stars.
About 80 percent of the stars in the Milky Way are red dwarfs, which, on average, are about one-third smaller and 4,000 degrees Fahrenheit cooler than the sun.
Kepler lead scientist William Borucki, with NASA's Ames Research Center in Mountain View, California, said he's not surprised by the finding of the European team, which uses a light-splitting spectrograph called HARPS on a telescope at the La Silla Observatory in Chile to look for planets beyond the solar system.
But claiming that red dwarfs' planets are rocky worlds goes too far, Borucki told Discovery News.
"I am astounded that they're saying they are rocky planets. I don't see any reason to assume they're rocky planets," Borucki said.
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Limits of the technology used by the HARPS team, which looks for slight wobbles in starlight caused by an orbiting planet's gravity, make assessments of a planet's density difficult, if not impossible, to determine. The Kepler team, which finds planets as they pass across their parent star's face relative to the telescope's line of sight, likewise is limited by its technique.